gadt13.hs:15:13: error:
    • Couldn't match expected type ‘p’
                  with actual type ‘String -> [Char]’
        ‘p’ is untouchable
          inside the constraints: a ~ Int
          bound by a pattern with constructor: I :: Int -> Term Int,
                   in an equation for ‘shw’
          at gadt13.hs:15:6-8
      ‘p’ is a rigid type variable bound by
        the inferred type of shw :: Term a -> p at gadt13.hs:15:1-30
      Possible fix: add a type signature for ‘shw’
    • Possible cause: ‘(.)’ is applied to too many arguments
      In the expression: ("I " ++) . shows t
      In an equation for ‘shw’: shw (I t) = ("I " ++) . shows t
    • Relevant bindings include
        shw :: Term a -> p (bound at gadt13.hs:15:1)